In many situations the physiology or pharmacology of an animal process is well enough understood that it can be manipulated by active ingredients such as hormones, drugs and minerals, but the exploitation is limited by the lack of practical methods of administering the active ingredients.
For example, oestrus synchronisation by progestogens in sheep and cattle has been known for more than 30 years but neither injection or feeding sheep or cows is a practical procedure especially under pastoral conditions.
As well as the practical difficulties involved in the administration of drugs, the question of residues is becoming increasingly important. In many cases it is unacceptable to the Authorities, such as the Animal Remedies Board to have animals injected with drugs. The question of possible residues of substances after injection is an increasing concern to such Authorities. This concern may be amplified by restrictions imposed overseas by the U.S. Federal Drug Administration and its E.E.C. equivalents. An outstanding example of this is the banning of stilboestrol in the U.S. despite the fact that carcass residues have never been demonstrated.
The present invention in the preferred form proposes the incorporation of an active ingredient in the skin of a two part device having a body and the skin and for example the active ingredient may be progesterone or an oestrogen or a mineral trace element such as selenium cobalt and copper and boron.